/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.binary;

import com.mlizhi.base.codec.BinaryDecoder;
import com.mlizhi.base.codec.BinaryEncoder;
import com.mlizhi.base.codec.DecoderException;
import com.mlizhi.base.codec.EncoderException;

import java.math.BigInteger;



/**
 * Provides Base64 encoding and decoding as defined by RFC 2045.
 * 
 * <p>
 * This class implements section <cite>6.8. Base64 Content-Transfer-Encoding</cite> from RFC 2045 <cite>Multipurpose
 * Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein.
 * </p>
 * <p>
 * The class can be parameterized in the following manner with various constructors:
 * <ul>
 * <li>URL-safe mode: Default off.</li>
 * <li>Line length: Default 76. Line length that aren't multiples of 4 will still essentially end up being multiples of
 * 4 in the encoded data.
 * <li>Line separator: Default is CRLF ("\r\n")</li>
 * </ul>
 * </p>
 * <p>
 * Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode
 * character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>
 * @author Apache Software Foundation
 * @since 1.0
 * @version $Id: Base64.java 801706 2009-08-06 16:27:06Z niallp $
 */
public class Base64 implements BinaryEncoder, BinaryDecoder {
private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;

private static final int DEFAULT_BUFFER_SIZE = 8192;

/**
 * Chunk size per RFC 2045 section 6.8.
 * 
 * <p>
 * The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
 * equal signs.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
 */
static final int CHUNK_SIZE = 76;

/**
 * Chunk separator per RFC 2045 section 2.1.
 *
 * <p>
 * N.B. The next major release may break compatibility and make this field private.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
 */
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};

/**
 * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
 * equivalents as specified in Table 1 of RFC 2045.
 * 
 * Thanks to "commons" project in ws.apache.org for this code.
 * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
 */
private static final byte[] STANDARD_ENCODE_TABLE = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

/**
 * This is a copy of the STANDARD_ENCODE_TABLE above, but with + and /
 * changed to - and _ to make the encoded Base64 results more URL-SAFE.
 * This table is only used when the Base64's mode is set to URL-SAFE.
 */
private static final byte[] URL_SAFE_ENCODE_TABLE = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'
};

/**
 * Byte used to pad output.
 */
private static final byte PAD = '=';

/**
 * This array is a lookup table that translates Unicode characters drawn from the "Base64 Alphabet" (as specified in
 * Table 1 of RFC 2045) into their 6-bit positive integer equivalents. Characters that are not in the Base64
 * alphabet but fall within the bounds of the array are translated to -1.
 * 
 * Note: '+' and '-' both decode to 62. '/' and '_' both decode to 63. This means decoder seamlessly handles both
 * URL_SAFE and STANDARD base64. (The encoder, on the other hand, needs to know ahead of time what to emit).
 * 
 * Thanks to "commons" project in ws.apache.org for this code.
 * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
 */
private static final byte[] DECODE_TABLE = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63, 52, 53, 54,
55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
};

/** Mask used to extract 6 bits, used when encoding */
private static final int MASK_6BITS = 0x3f;

/** Mask used to extract 8 bits, used in decoding base64 bytes */
private static final int MASK_8BITS = 0xff;

// The static final fields above are used for the original static byte[] methods on Base64.
// The private member fields below are used with the new streaming approach, which requires
// some state be preserved between calls of encode() and decode().

/**
 * Encode table to use: either STANDARD or URL_SAFE. Note: the DECODE_TABLE above remains static because it is able
 * to decode both STANDARD and URL_SAFE streams, but the encodeTable must be a member variable so we can switch
 * between the two modes.
 */
private final byte[] encodeTable;

/**
 * Line length for encoding. Not used when decoding. A value of zero or less implies no chunking of the base64
 * encoded data.
 */
private final int lineLength;

/**
 * Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
 */
private final byte[] lineSeparator;

/**
 * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
 * <code>decodeSize = 3 + lineSeparator.length;</code>
 */
private final int decodeSize;

/**
 * Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
 * <code>encodeSize = 4 + lineSeparator.length;</code>
 */
private final int encodeSize;

/**
 * Buffer for streaming.
 */
private byte[] buffer;

/**
 * Position where next character should be written in the buffer.
 */
private int pos;

/**
 * Position where next character should be read from the buffer.
 */
private int readPos;

/**
 * Variable tracks how many characters have been written to the current line. Only used when encoding. We use it to
 * make sure each encoded line never goes beyond lineLength (if lineLength > 0).
 */
private int currentLinePos;

/**
 * Writes to the buffer only occur after every 3 reads when encoding, an every 4 reads when decoding. This variable
 * helps track that.
 */
private int modulus;

/**
 * Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this Base64 object becomes useless,
 * and must be thrown away.
 */
private boolean eof;

/**
 * Place holder for the 3 bytes we're dealing with for our base64 logic. Bitwise operations store and extract the
 * base64 encoding or decoding from this variable.
 */
private int x;

/**
 * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
 * <p>
 * When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
 * </p>
 * 
 * <p>
 * When decoding all variants are supported.
 * </p>
 */
public Base64() {
this(false);
}

/**
 * Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.
 * <p>
 * When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
 * </p>
 * 
 * <p>
 * When decoding all variants are supported.
 * </p>
 * 
 * @param urlSafe
 *if <code>true</code>, URL-safe encoding is used. In most cases this should be set to
 *<code>false</code>.
 * @since 1.4
 */
public Base64(boolean urlSafe) {
this(CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
}

/**
 * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
 * <p>
 * When encoding the line length is given in the constructor, the line separator is CRLF, and the encoding table is
 * STANDARD_ENCODE_TABLE.
 * </p>
 * <p>
 * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
 * </p>
 * <p>
 * When decoding all variants are supported.
 * </p>
 * 
 * @param lineLength
 *Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
 *If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
 * @since 1.4
 */
public Base64(int lineLength) {
this(lineLength, CHUNK_SEPARATOR);
}

/**
 * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
 * <p>
 * When encoding the line length and line separator are given in the constructor, and the encoding table is
 * STANDARD_ENCODE_TABLE.
 * </p>
 * <p>
 * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
 * </p>
 * <p>
 * When decoding all variants are supported.
 * </p>
 * 
 * @param lineLength
 *Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
 *If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
 * @param lineSeparator
 *Each line of encoded data will end with this sequence of bytes.
 * @throws IllegalArgumentException
 * Thrown when the provided lineSeparator included some base64 characters.
 * @since 1.4
 */
public Base64(int lineLength, byte[] lineSeparator) {
this(lineLength, lineSeparator, false);
}

/**
 * Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
 * <p>
 * When encoding the line length and line separator are given in the constructor, and the encoding table is
 * STANDARD_ENCODE_TABLE.
 * </p>
 * <p>
 * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
 * </p>
 * <p>
 * When decoding all variants are supported.
 * </p>
 * 
 * @param lineLength
 *Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
 *If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
 * @param lineSeparator
 *Each line of encoded data will end with this sequence of bytes.
 * @param urlSafe
 *Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode
 *operations. Decoding seamlessly handles both modes.
 * @throws IllegalArgumentException
 * The provided lineSeparator included some base64 characters. That's not going to work!
 * @since 1.4
 */
public Base64(int lineLength, byte[] lineSeparator, boolean urlSafe) {
if (lineSeparator == null) {
lineLength = 0;  // disable chunk-separating
lineSeparator = CHUNK_SEPARATOR;  // this just gets ignored
}
this.lineLength = lineLength > 0 ? (lineLength / 4) * 4 : 0;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
if (lineLength > 0) {
this.encodeSize = 4 + lineSeparator.length;
} else {
this.encodeSize = 4;
}
this.decodeSize = this.encodeSize - 1;
if (containsBase64Byte(lineSeparator)) {
String sep = StringUtils.newStringUtf8(lineSeparator);
throw new IllegalArgumentException("lineSeperator must not contain base64 characters: [" + sep + "]");
}
this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
}

/**
 * Returns our current encode mode. True if we're URL-SAFE, false otherwise.
 * 
 * @return true if we're in URL-SAFE mode, false otherwise.
 * @since 1.4
 */
public boolean isUrlSafe() {
return this.encodeTable == URL_SAFE_ENCODE_TABLE;
}

/**
 * Returns true if this Base64 object has buffered data for reading.
 * 
 * @return true if there is Base64 object still available for reading.
 */
boolean hasData() {
return this.buffer != null;
}

/**
 * Returns the amount of buffered data available for reading.
 * 
 * @return The amount of buffered data available for reading.
 */
int avail() {
return buffer != null ? pos - readPos : 0;
}

/** Doubles our buffer. */
private void resizeBuffer() {
if (buffer == null) {
buffer = new byte[DEFAULT_BUFFER_SIZE];
pos = 0;
readPos = 0;
} else {
byte[] b = new byte[buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
System.arraycopy(buffer, 0, b, 0, buffer.length);
buffer = b;
}
}

/**
 * Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
 * bytes. Returns how many bytes were actually extracted.
 * 
 * @param b
 *byte[] array to extract the buffered data into.
 * @param bPos
 *position in byte[] array to start extraction at.
 * @param bAvail
 *amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
 * @return The number of bytes successfully extracted into the provided byte[] array.
 */
int readResults(byte[] b, int bPos, int bAvail) {
if (buffer != null) {
int len = Math.min(avail(), bAvail);
if (buffer != b) {
System.arraycopy(buffer, readPos, b, bPos, len);
readPos += len;
if (readPos >= pos) {
buffer = null;
}
} else {
// Re-using the original consumer's output array is only
// allowed for one round.
buffer = null;
}
return len;
}
return eof ? -1 : 0;
}

/**
 * Sets the streaming buffer. This is a small optimization where we try to buffer directly to the consumer's output
 * array for one round (if the consumer calls this method first) instead of starting our own buffer.
 * 
 * @param out
 *byte[] array to buffer directly to.
 * @param outPos
 *Position to start buffering into.
 * @param outAvail
 *Amount of bytes available for direct buffering.
 */
void setInitialBuffer(byte[] out, int outPos, int outAvail) {
// We can re-use consumer's original output array under
// special circumstances, saving on some System.arraycopy().
if (out != null && out.length == outAvail) {
buffer = out;
pos = outPos;
readPos = outPos;
}
}

/**
 * <p>
 * Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
 * the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
 * remaining bytes (if not multiple of 3).
 * </p>
 * <p>
 * Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
 * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
 * </p>
 * 
 * @param in
 *byte[] array of binary data to base64 encode.
 * @param inPos
 *Position to start reading data from.
 * @param inAvail
 *Amount of bytes available from input for encoding.
 */
void encode(byte[] in, int inPos, int inAvail) {
if (eof) {
return;
}
// inAvail < 0 is how we're informed of EOF in the underlying data we're
// encoding.
if (inAvail < 0) {
eof = true;
if (buffer == null || buffer.length - pos < encodeSize) {
resizeBuffer();
}
switch (modulus) {
case 1 :
buffer[pos++] = encodeTable[(x >> 2) & MASK_6BITS];
buffer[pos++] = encodeTable[(x << 4) & MASK_6BITS];
// URL-SAFE skips the padding to further reduce size.
if (encodeTable == STANDARD_ENCODE_TABLE) {
buffer[pos++] = PAD;
buffer[pos++] = PAD;
}
break;

case 2 :
buffer[pos++] = encodeTable[(x >> 10) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 4) & MASK_6BITS];
buffer[pos++] = encodeTable[(x << 2) & MASK_6BITS];
// URL-SAFE skips the padding to further reduce size.
if (encodeTable == STANDARD_ENCODE_TABLE) {
buffer[pos++] = PAD;
}
break;
}
if (lineLength > 0 && pos > 0) {
System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
pos += lineSeparator.length;
}
} else {
for (int i = 0; i < inAvail; i++) {
if (buffer == null || buffer.length - pos < encodeSize) {
resizeBuffer();
}
modulus = (++modulus) % 3;
int b = in[inPos++];
if (b < 0) {
b += 256;
}
x = (x << 8) + b;
if (0 == modulus) {
buffer[pos++] = encodeTable[(x >> 18) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 12) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 6) & MASK_6BITS];
buffer[pos++] = encodeTable[x & MASK_6BITS];
currentLinePos += 4;
if (lineLength > 0 && lineLength <= currentLinePos) {
System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
pos += lineSeparator.length;
currentLinePos = 0;
}
}
}
}
}

/**
 * <p>
 * Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
 * with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
 * call is not necessary when decoding, but it doesn't hurt, either.
 * </p>
 * <p>
 * Ignores all non-base64 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
 * silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
 * garbage-out philosophy: it will not check the provided data for validity.
 * </p>
 * <p>
 * Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
 * http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
 * </p>
 * 
 * @param in
 *byte[] array of ascii data to base64 decode.
 * @param inPos
 *Position to start reading data from.
 * @param inAvail
 *Amount of bytes available from input for encoding.
 */
void decode(byte[] in, int inPos, int inAvail) {
if (eof) {
return;
}
if (inAvail < 0) {
eof = true;
}
for (int i = 0; i < inAvail; i++) {
if (buffer == null || buffer.length - pos < decodeSize) {
resizeBuffer();
}
byte b = in[inPos++];
if (b == PAD) {
// We're done.
eof = true;
break;
} else {
if (b >= 0 && b < DECODE_TABLE.length) {
int result = DECODE_TABLE[b];
if (result >= 0) {
modulus = (++modulus) % 4;
x = (x << 6) + result;
if (modulus == 0) {
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
buffer[pos++] = (byte) (x & MASK_8BITS);
}
}
}
}
}

// Two forms of EOF as far as base64 decoder is concerned: actual
// EOF (-1) and first time '=' character is encountered in stream.
// This approach makes the '=' padding characters completely optional.
if (eof && modulus != 0) {
x = x << 6;
switch (modulus) {
case 2 :
x = x << 6;
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
break;
case 3 :
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
break;
}
}
}

/**
 * Returns whether or not the <code>octet</code> is in the base 64 alphabet.
 * 
 * @param octet
 *The value to test
 * @return <code>true</code> if the value is defined in the the base 64 alphabet, <code>false</code> otherwise.
 * @since 1.4
 */
public static boolean isBase64(byte octet) {
return octet == PAD || (octet >= 0 && octet < DECODE_TABLE.length && DECODE_TABLE[octet] != -1);
}

/**
 * Tests a given byte array to see if it contains only valid characters within the Base64 alphabet. Currently the
 * method treats whitespace as valid.
 * 
 * @param arrayOctet
 *byte array to test
 * @return <code>true</code> if all bytes are valid characters in the Base64 alphabet or if the byte array is empty;
 * false, otherwise
 */
public static boolean isArrayByteBase64(byte[] arrayOctet) {
for (int i = 0; i < arrayOctet.length; i++) {
if (!isBase64(arrayOctet[i]) && !isWhiteSpace(arrayOctet[i])) {
return false;
}
}
return true;
}

/**
 * Tests a given byte array to see if it contains only valid characters within the Base64 alphabet.
 * 
 * @param arrayOctet
 *byte array to test
 * @return <code>true</code> if any byte is a valid character in the Base64 alphabet; false herwise
 */
private static boolean containsBase64Byte(byte[] arrayOctet) {
for (int i = 0; i < arrayOctet.length; i++) {
if (isBase64(arrayOctet[i])) {
return true;
}
}
return false;
}

/**
 * Encodes binary data using the base64 algorithm but does not chunk the output.
 * 
 * @param binaryData
 *binary data to encode
 * @return byte[] containing Base64 characters in their UTF-8 representation.
 */
public static byte[] encodeBase64(byte[] binaryData) {
return encodeBase64(binaryData, false);
}

/**
 * Encodes binary data using the base64 algorithm into 76 character blocks separated by CRLF.
 *
 * @param binaryData
 *binary data to encode
 * @return String containing Base64 characters.
 * @since 1.4
 */
public static String encodeBase64String(byte[] binaryData) {
return StringUtils.newStringUtf8(encodeBase64(binaryData, true));
}

/**
 * Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
 * url-safe variation emits - and _ instead of + and / characters.
 * 
 * @param binaryData
 *binary data to encode
 * @return byte[] containing Base64 characters in their UTF-8 representation.
 * @since 1.4
 */
public static byte[] encodeBase64URLSafe(byte[] binaryData) {
return encodeBase64(binaryData, false, true);
}

/**
 * Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The
 * url-safe variation emits - and _ instead of + and / characters.
 *
 * @param binaryData
 *binary data to encode
 * @return String containing Base64 characters
 * @since 1.4
 */
public static String encodeBase64URLSafeString(byte[] binaryData) {
return StringUtils.newStringUtf8(encodeBase64(binaryData, false, true));
}

/**
 * Encodes binary data using the base64 algorithm and chunks the encoded output into 76 character blocks
 * 
 * @param binaryData
 *binary data to encode
 * @return Base64 characters chunked in 76 character blocks
 */
public static byte[] encodeBase64Chunked(byte[] binaryData) {
return encodeBase64(binaryData, true);
}

/**
 * Decodes an Object using the base64 algorithm. This method is provided in order to satisfy the requirements of the
 * Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
 * 
 * @param pObject
 *Object to decode
 * @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String supplied.
 * @throws DecoderException
 * if the parameter supplied is not of type byte[]
 */
public Object decode(Object pObject) throws DecoderException {
if (pObject instanceof byte[]) {
return decode((byte[]) pObject);
} else if (pObject instanceof String) {
return decode((String) pObject);
} else {
throw new DecoderException("Parameter supplied to Base64 decode is not a byte[] or a String");
}
}

/**
 * Decodes a String containing containing characters in the Base64 alphabet.
 *
 * @param pArray
 *A String containing Base64 character data
 * @return a byte array containing binary data
 * @since 1.4
 */
public byte[] decode(String pArray) {
return decode(StringUtils.getBytesUtf8(pArray));
}

/**
 * Decodes a byte[] containing containing characters in the Base64 alphabet.
 * 
 * @param pArray
 *A byte array containing Base64 character data
 * @return a byte array containing binary data
 */
public byte[] decode(byte[] pArray) {
reset();
if (pArray == null || pArray.length == 0) {
return pArray;
}
long len = (pArray.length * 3) / 4;
byte[] buf = new byte[(int) len];
setInitialBuffer(buf, 0, buf.length);
decode(pArray, 0, pArray.length);
decode(pArray, 0, -1); // Notify decoder of EOF.

// Would be nice to just return buf (like we sometimes do in the encode
// logic), but we have no idea what the line-length was (could even be
// variable).  So we cannot determine ahead of time exactly how big an
// array is necessary.  Hence the need to construct a 2nd byte array to
// hold the final result:

byte[] result = new byte[pos];
readResults(result, 0, result.length);
return result;
}

/**
 * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
 * 
 * @param binaryData
 *Array containing binary data to encode.
 * @param isChunked
 *if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
 * @return Base64-encoded data.
 * @throws IllegalArgumentException
 * Thrown when the input array needs an output array bigger than {@link Integer#MAX_VALUE}
 */
public static byte[] encodeBase64(byte[] binaryData, boolean isChunked) {
return encodeBase64(binaryData, isChunked, false);
}

/**
 * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
 * 
 * @param binaryData
 *Array containing binary data to encode.
 * @param isChunked
 *if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
 * @param urlSafe
 *if <code>true</code> this encoder will emit - and _ instead of the usual + and / characters.
 * @return Base64-encoded data.
 * @throws IllegalArgumentException
 * Thrown when the input array needs an output array bigger than {@link Integer#MAX_VALUE}
 * @since 1.4
 */
public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe) {
return encodeBase64(binaryData, isChunked, urlSafe, Integer.MAX_VALUE);
}

/**
 * Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
 * 
 * @param binaryData
 *Array containing binary data to encode.
 * @param isChunked
 *if <code>true</code> this encoder will chunk the base64 output into 76 character blocks
 * @param urlSafe
 *if <code>true</code> this encoder will emit - and _ instead of the usual + and / characters.
 * @param maxResultSize
 *The maximum result size to accept.
 * @return Base64-encoded data.
 * @throws IllegalArgumentException
 * Thrown when the input array needs an output array bigger than maxResultSize
 * @since 1.4
 */
public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize) {
if (binaryData == null || binaryData.length == 0) {
return binaryData;
}

long len = getEncodeLength(binaryData, CHUNK_SIZE, CHUNK_SEPARATOR);
if (len > maxResultSize) {
throw new IllegalArgumentException("Input array too big, the output array would be bigger (" +
len +
") than the specified maxium size of " +
maxResultSize);
}

Base64 b64 = isChunked ? new Base64(urlSafe) : new Base64(0, CHUNK_SEPARATOR, urlSafe);
return b64.encode(binaryData);
}

/**
 * Decodes a Base64 String into octets
 *
 * @param base64String
 *String containing Base64 data
 * @return Array containing decoded data.
 * @since 1.4
 */
public static byte[] decodeBase64(String base64String) {
return new Base64().decode(base64String);
}

/**
 * Decodes Base64 data into octets
 * 
 * @param base64Data
 *Byte array containing Base64 data
 * @return Array containing decoded data.
 */
public static byte[] decodeBase64(byte[] base64Data) {
return new Base64().decode(base64Data);
}

/**
 * Discards any whitespace from a base-64 encoded block.
 * 
 * @param data
 *The base-64 encoded data to discard the whitespace from.
 * @return The data, less whitespace (see RFC 2045).
 * @deprecated This method is no longer needed
 */
static byte[] discardWhitespace(byte[] data) {
byte groomedData[] = new byte[data.length];
int bytesCopied = 0;
for (int i = 0; i < data.length; i++) {
switch (data[i]) {
case ' ' :
case '\n' :
case '\r' :
case '\t' :
break;
default :
groomedData[bytesCopied++] = data[i];
}
}
byte packedData[] = new byte[bytesCopied];
System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);
return packedData;
}

/**
 * Checks if a byte value is whitespace or not.
 * 
 * @param byteToCheck
 *the byte to check
 * @return true if byte is whitespace, false otherwise
 */
private static boolean isWhiteSpace(byte byteToCheck) {
switch (byteToCheck) {
case ' ' :
case '\n' :
case '\r' :
case '\t' :
return true;
default :
return false;
}
}

// Implementation of the Encoder Interface

/**
 * Encodes an Object using the base64 algorithm. This method is provided in order to satisfy the requirements of the
 * Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
 * 
 * @param pObject
 *Object to encode
 * @return An object (of type byte[]) containing the base64 encoded data which corresponds to the byte[] supplied.
 * @throws EncoderException
 * if the parameter supplied is not of type byte[]
 */
public Object encode(Object pObject) throws EncoderException {
if (!(pObject instanceof byte[])) {
throw new EncoderException("Parameter supplied to Base64 encode is not a byte[]");
}
return encode((byte[]) pObject);
}

/**
 * Encodes a byte[] containing binary data, into a String containing characters in the Base64 alphabet.
 *
 * @param pArray
 *a byte array containing binary data
 * @return A String containing only Base64 character data
 * @since 1.4
 */
public String encodeToString(byte[] pArray) {
return StringUtils.newStringUtf8(encode(pArray));
}

/**
 * Encodes a byte[] containing binary data, into a byte[] containing characters in the Base64 alphabet.
 * 
 * @param pArray
 *a byte array containing binary data
 * @return A byte array containing only Base64 character data
 */
public byte[] encode(byte[] pArray) {
reset();
if (pArray == null || pArray.length == 0) {
return pArray;
}
long len = getEncodeLength(pArray, lineLength, lineSeparator);
byte[] buf = new byte[(int) len];
setInitialBuffer(buf, 0, buf.length);
encode(pArray, 0, pArray.length);
encode(pArray, 0, -1); // Notify encoder of EOF.
// Encoder might have resized, even though it was unnecessary.
if (buffer != buf) {
readResults(buf, 0, buf.length);
}
// In URL-SAFE mode we skip the padding characters, so sometimes our
// final length is a bit smaller.
if (isUrlSafe() && pos < buf.length) {
byte[] smallerBuf = new byte[pos];
System.arraycopy(buf, 0, smallerBuf, 0, pos);
buf = smallerBuf;
}
return buf;
}

/**
 * Pre-calculates the amount of space needed to base64-encode the supplied array.
 *
 * @param pArray byte[] array which will later be encoded
 * @param chunkSize line-length of the output (<= 0 means no chunking) between each
 *chunkSeparator (e.g. CRLF).
 * @param chunkSeparator the sequence of bytes used to separate chunks of output (e.g. CRLF).
 *
 * @return amount of space needed to encoded the supplied array.  Returns
 * a long since a max-len array will require Integer.MAX_VALUE + 33%.
 */
private static long getEncodeLength(byte[] pArray, int chunkSize, byte[] chunkSeparator) {
// base64 always encodes to multiples of 4.
chunkSize = (chunkSize / 4) * 4;

long len = (pArray.length * 4) / 3;
long mod = len % 4;
if (mod != 0) {
len += 4 - mod;
}
if (chunkSize > 0) {
boolean lenChunksPerfectly = len % chunkSize == 0;
len += (len / chunkSize) * chunkSeparator.length;
if (!lenChunksPerfectly) {
len += chunkSeparator.length;
}
}
return len;
}

// Implementation of integer encoding used for crypto
/**
 * Decodes a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
 * 
 * @param pArray
 *a byte array containing base64 character data
 * @return A BigInteger
 * @since 1.4
 */
public static BigInteger decodeInteger(byte[] pArray) {
return new BigInteger(1, decodeBase64(pArray));
}

/**
 * Encodes to a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
 * 
 * @param bigInt
 *a BigInteger
 * @return A byte array containing base64 character data
 * @throws NullPointerException
 * if null is passed in
 * @since 1.4
 */
public static byte[] encodeInteger(BigInteger bigInt) {
if (bigInt == null) {
throw new NullPointerException("encodeInteger called with null parameter");
}
return encodeBase64(toIntegerBytes(bigInt), false);
}

/**
 * Returns a byte-array representation of a <code>BigInteger</code> without sign bit.
 * 
 * @param bigInt
 *<code>BigInteger</code> to be converted
 * @return a byte array representation of the BigInteger parameter
 */
static byte[] toIntegerBytes(BigInteger bigInt) {
int bitlen = bigInt.bitLength();
// round bitlen
bitlen = ((bitlen + 7) >> 3) << 3;
byte[] bigBytes = bigInt.toByteArray();

if (((bigInt.bitLength() % 8) != 0) && (((bigInt.bitLength() / 8) + 1) == (bitlen / 8))) {
return bigBytes;
}
// set up params for copying everything but sign bit
int startSrc = 0;
int len = bigBytes.length;

// if bigInt is exactly byte-aligned, just skip signbit in copy
if ((bigInt.bitLength() % 8) == 0) {
startSrc = 1;
len--;
}
int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
byte[] resizedBytes = new byte[bitlen / 8];
System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);
return resizedBytes;
}

/**
 * Resets this Base64 object to its initial newly constructed state.
 */
private void reset() {
buffer = null;
pos = 0;
readPos = 0;
currentLinePos = 0;
modulus = 0;
eof = false;
}

}
